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PYONGYANG, North Korea — North Korea bragged Wednesday about the “spectacular success” of its first ever hydrogen bomb test, a defiant act that leader Kim Jong Un — in a statement read on state television — said would “make the world … look up to our strong nuclear country.”

But did it really happen?

The United States doesn’t think so, with White House spokesman Josh Earnest saying “the initial analysis is not consistent with the North Korean claims.”

That analysis isn’t definitive, though, with some experts saying it’s possible that Pyongyang detonated a different type of hydrogen bomb. And even if it wasn’t an H-bomb, there’s little doubt that North Korea did conduct a new significant nuclear test despite persistent calls not to do so.

The underground test, which happened at 10 a.m. (8:30 p.m. ET Tuesday), corresponded with a magnitude-5.1 seismic event centered 12 miles (19 kilometers) east-southeast of Sungjibaegam, according to the U.S. Geological Survey. That’s comparable to readings from North Korea’s most recent plutonium test in 2013.

Norsar, a Norway-based group that monitors nuclear tests, noted this fact and estimated, based on the seismic readings, a blast equivalent to less than of 10,000 tons of TNT — smaller than those of the atomic bombs used on Hiroshima and Nagasaki, and far less than thermonuclear weapons that typically are as potent as millions of tons of TNT.

“We won’t know for another few days or weeks whether this was (a hydrogen bomb),” said Martin Navias, a military expert at King’s College London. “It doesn’t look like one; … one would have expected it to be greater if it was an H-bomb.”

U.S. or South Korean experts may have an answer soon after analyzing the atmosphere for trace elements of radiation. Yet Mike Chinoy, a fellow at the University of Southern California’s U.S.-China Institute, noted that “we may never know 100%.”

After being briefed by his nation’s military, South Korean lawmaker Shin Kyung-min questioned the credibility of the hydrogen bomb claim. Joo Ho-young, who heard from the nation’s intelligence service, told reporters “it could different from a usual hydrogen bomb.”

Count Bruce Bennett, a senior defense analyst at the nonpartisan Rand research group, among the skeptics. He said North Korea has had trouble “mastering even the basics of a fission weapon,” so it’s a big leap to think it could create an even more complicated hydrogen bomb.

Whether or not it’s a hydrogen bomb, the test did get the world’s attention.

“Any kind of nuclear test, like the one that North Korea conducted … is provocative and a flagrant violation of United Nations Security Council resolutions,” said Earnest.

Will the world stop North Korea?

And that — sticking it to world and regional powers — may be Pyongyang’s aim.

“The present-day grim reality clearly proves once again the immutable truth that one’s destiny should be defended by one’s own efforts,” North Korea’s official KCNA news agency reported. “… The army and people of the DPRK will steadily escalate its nuclear deterrence of justice both in quality and quantity to reliably guarantee the future of the revolutionary cause.”

The United Nations Security Council held a closed-door meeting Wednesday geared to preventing Pyongyang from getting more nuclear weapons and punishing it for the test earlier that day.

Past U.N. measures included arms, nonproliferation and luxury good embargoes, a freeze on overseas financial assets and a travel ban. None of them stopped North Korea from continuing its nuclear program. So what’s to say whatever the world community does now — if anything — will change that?

After Wednesday’s meeting, the 15-member U.N. Security Council (which includes China, Russia and the United States) together condemned the test as a “clear violation of (past) resolutions … and of the non-proliferation regime.”

“The members of the Security Council also (express) determination to take further significant measures in the event of another DPRK nuclear test,” the council statement continued. “And in line with this commitment and the gravity of this violation, the members of the Security Council will begin to work immediately on such measures in a new Security Council resolution.”

Japan’s ambassador to the U.N., Motohide Yoshikawa, said his country was calling for a robust resolution to be adopted swiftly.

Victor Cha, a Georgetown University professor and National Security Council Asian affairs director during the George W. Bush administration, called China critical to making sure sanctions are effective. He questioned its willingness to do so up to now, given concerns about fostering instability in a neighboring nation.

“They (have) not (been) willing to really step on the North Koreans’ necks to get them to give up these weapons,” Cha said of the Chinese.

China did speak out strongly against the latest test, saying it had no advance notice. Beijing had company, as leaders from around the world, including Russia and NATO, condemned it — rare unanimity at a time of pervasive discord on issues like Syria’s civil war, the Shiite-Sunni Muslim divide, Ukraine and migration.

The anger and danger were felt most in South Korea, which was split from the North seven decades ago.

“This is clearly a provocation and threatening the lives of people and safety,” South Korean President Park Geun-hye said. “We have been continuously warning that (North Korea) will pay a price for conducting a nuclear test.”

Test puts U.S. ‘on the spot’

In its official statements, Pyongyang singled out the United States — or, as it called it, “a gang of cruel robbers” and a “hideous nuclear criminal that has constantly posed nuclear blackmail for more than 70 years, seriously endangering mankind.” North Korea not only has a “legitimate right” to have nuclear weapons, they’re needed as a deterrent to Washington’s “deep-rooted, harsh and … hostile policy,” according to these reports.

“The spectacular success … in the H-bomb test (is) a historic event of … national significance as it surely guarantees the eternal future of the nation,” the KCNA story stated.

Charged anti-American rhetoric is hardly unusual for the authoritarian Asian nation, though it takes on a different tone when paired with nuclear boasts.

Chinoy, the U.S.-China Institute fellow, pointed out that three of North Korea’s four nuclear tests — in 2009, 2013 and now — have taken place during the tenure of U.S. President Barack Obama, who’s made progress on curtailing Iran’s atomic aspirations but not North Korea’s.

This latest one, in particular, “puts the U.S. on the spot,” according to Chinoy.

“Will any of their steps do anything to restrain North Korea?” the analyst mused. “My guess is probably not.”

A heavily militarized state

Combined with its secrecy and seclusion, North Korea’s us-against-the-world perspective and the fact it doesn’t play by traditional rules make it unpredictable at best and dangerous at worst. Add nuclear weapons to the mix — even if they aren’t thermonuclear — and Pyongyang could unleash devastation of a sort not seen in over 70 years.

That’s when U.S. forces used atomic bombs on the Japanese cities of Hiroshima and Nagasaki, ending World War II. Minuscule in power compared with H-bombs, the two blasts nonetheless killed about 200,000 people.

While it’s done little outwardly to develop its economy, North Korea has put a lot of focus on its military, carrying a huge standing army of 1.2 million active soldiers plus 7.7 million reservists in a country of 25 million people.

“If a nuclear device has been detonated … it underlines the very real threat that North Korea represents to regional and international security,” British Foreign Secretary Philip Hammond said.

Last May, North Korea claimed it had the ability to miniaturize nuclear weapons, a development that would allow it to deploy nuclear weapons on missiles. A U.S. National Security Council spokesman responded at the time that the United States did not think the North Koreans had such a capability.

Still, the possibility of Pyongyang being able to strike the U.S. mainland, even now, can’t be ruled out. And there’s no doubt that South Korea and Japan — two countries that Washington has long vowed to defend — are within reach.

David Albright, a former U.N. weapons inspector, told CNN last year that Pyongyang could already have 10 to 15 atomic weapons, and that it could grow that amount by several weapons per year.

He believed then that Pyongyang could miniaturize a warhead for shorter missiles, but not yet for intercontinental ballistic missiles capable of reaching the United States.

Albright called the latest nuclear test “largely a mystery” and surmised that North Korea didn’t test a standard two-stage hydrogen bomb, in which an atomic blast sets off a thermonuclear explosion. He said it’s possible that “another thermonuclear weapon design” was tested, noting there “are many types of such weapons” that “can achieve very high explosive yields.”

“North Korea can bluff,” said Albright, the founder of the Institute for Science and International Security. “It can claim that it now knows how to achieve high yields with thermonuclear concepts. It is difficult to prove it does not.”